Machine screw anchor



June 1938. M. L. SCHULTE MACHINE SCREW ANCHOR Filed March 5 INVENTOR 2 BY dlfifif fi f ATTORNEY Patented June 14, 1938 PATENT OFFICE I 2.120.517 MACHINE sonnw ANCHOR Max L. Schulte, Ridgewood, N. J., assignor to The Rawlplug Company, Inc., New York, N. Y.

Application March 5, 1937, Serial No. 129,198

9 Claims. (Cl. 72-105) This invention relates to an expansible anchor, particularly adapted for machine screws or studs havingmachine screw threads thereon, and the like. Such anchors are used in attach ing various devices or fittings to materials like stone, brick, concrete or other hard materials which have to be drilled to receive the screw or stud anchor, which devices are expanded or caulked into place.

In drilling suchhard materials, the drills have to be frequently sharpened and they wear down rather rapidly in diameter, so that in the use of the same drill, the hole gradually becomes small-- er. For each size of screw or bolt anchor there is. a best size of-drill, the diameter of the anchor and that of the drill being chosen to give the best holding power by the anchor in the kind of material in which the anchor is used.

In the smaller sizes of anchors, the fits are usually closer; that is to say, the diameter of the drill and diameter of the anchor are very near each other, so --that after the hole has been drilled, the anchor can be readily pushed into position for the final caulking operation. However, as has been stated, as the drill wears, the hole becomes smaller, so that the anchor used cannot be put into the hole without using considerable force, which cannot be. used without distorting the mouldable metal of the anchor,

thereby rendering insertion into the hole impractical. Considerable force should be applied only after the anchor is inserted into the hole, and then applied by means of the caulking tool.

It is therefore the object of my invention to provide an anchor which will compensate for the wear on the drill.

Other ancillary objects will appear from a reading'of the specification, taken in connection with the annexed drawing, wherein:

Figure 1 is a perspective, elevational view of my improved form of anchor.

Figure 2 is a vertical, sectional view through the anchor on the plane 22 of Figure 1.

Figure 3is an end view of the anchor in a hole drilled with a new drill of standard size, and

before the anchor has been expanded or caulked into final position.

Figure 4 is a view similar to Figure 3, but showing a condition where the hole has been drilled with a worm drill.

Figure 5 is a view of the anchor shown in Figure 4 as it is being inserted into a hole.

Figure 6 shows a modified form of the expansible member comprising part of the anchor.

Figure 7 shows a further modified form 01' the same member.

Figure 8 shows a modified form of expanding member and which, in many cases, is the preferred form. 0

Figures 9 and 10 show further modified forms of an expansible member in which the outer surface projections may take different shapes.

Figure 11 shows a still further modified form of expansible member in which the outer surface 0 is broken up into a series of cones of increasing diameter toward the caulking end of the anchor. I

In the various views, wherein like numbers refer to corresponding parts, I is an expansible 15 member having a plurality of flutes 2 around the peripheral surface of said member. The member 1 fits telescopically over the expanding member 3, one end of which has a tapered surface 4 extending at least part-way of the length of the member 3. Preferably the tapered surface 4 is provided with knurls 5 that extend generally longitudinally of the member 3, and as shown in Figures 1 and 2. the member I has one end normally fitting onto the tapered surface 4 into engagement with the knurls 5. For shipping and handling purposes, the two mem hers I and 3 are forced together sufliciently to hold them in gripping relationship, so that the anchor may be handled as a unit. 30

The hole-entering end of the expanding member 3 is provided with a flange 6 which, as shown in Figure 8, is preferably extended at 1 radially beyond the beginning of the tapered surface 4, for the purpose of presenting more resistance to 5 the withdrawal of the anchor by the pull applied thereto through the screws holding the load or device held in place by the screws. The flange 6 also has a tendency to retard the flow of the softer expansible metal over the inner end of the 40 expanding member during the'caulklng operation.

In either construction of Figure 2 or 8, the flange 6 is of smaller diameter than the outer boundary surface of the -fiutes 2, and preferably 45 of smaller diameter than that of a drill suitable for a given anchor at the end of the life of the drill. By way of illustration but not of limitation, this diameter may be from V5 to 3 smaller, depending on the size of the anchor to and the use to which it is to be put. The object of this will be directly explained.

In Figure 3, a hole 8 is shown in the material 9, and the-anchor shown in Figure 1 is shown in position therein. In this case, the diameter across the edges of the flutes 2 is no greater than the diameter of the hole 8, so that the anchor may be very readily passed into position. After the anchor is put in place, a tool, having a pilot thereon to enter the tapped hole l0 in the expanding member 3, is applied to the outer end of the expansible member I, usually of lead, and by hammer blows on the end of the tool, which has an annular shank to fit substantially the entire end of the member I, the member I is driven onto the tapered surface 4 and is caused to expand into gripping engagement with the wall of the hole.

The longitudinally arranged knurls 5 are to prevent the hard metal cone or expanding member 6 from turning in the soft expansible metal, such as lead, when the fastening screw is turned up tight in the anchor. The knurls may also assist in spreading the expansible member I.

As shown in the various figures, the flutes 2 have been exaggerated in size to better illustrate the idea. In practice, these flutes are very much smaller and greater in number than those shown in the different views.

In Figure 5, the hole 8 has been made with a drill that is worn down in diameter, but there still is a clearance for the flange 6 on the expanding member. However, it will be seen that the edges of the flutes 2 strike the peripheral edge of the hole 8, but a slight pressure or tapping on the outer end of the member I will cause the edges of the flutes 2 to either be sheared off or rolled over as indicated at H in Figure 4. After the insertion of the anchor, it is then caulked into place as previously described.

The hole-entering end of the expanding member 3 has a relatively large counter-bore or recess l2 therein with a tapered opening l3 leading into the recess I 2. The purpose of this recess and the opening I3 is to provide a receptacle or chamber for thedust and chips which may be in the hole when the anchor is caulked into place. If it were not for this large recess, some of the dust and chips might be forced into the threaded hole 10, which would cause trouble in applying the screw or stud used to hold the device or attachment to the surface in which the anchor has been located.

The flutes may be-- arranged in a number of ways; for example, in Figure 6 the flutes or corrugations are shown arranged in a helical manner on member I, the-pitch of the helix being varied as desired.

In Figure 7 the flutes or corrugations are transversely arranged.-

In Figure 9 the flutes take the form of pointed projections l4.

In Figure 10 the projections may be polygonal in shape, small pyramidal squares I5 being shown, but in any case, these flutes or projecting portions permit forcing the anchor into a hole in masonry or the like of closer dimensions than the anchor, without distorting the same.

In Figure 11, the projecting portions are -in the form of substantially transversely spaced flutes i6 which increase in diameter toward the drive end of the anchor, so that only the last few or outer flutes will engage the wall of the hole and be turned over or collapsed in the spaces behind them. With this arrangement, exceedingly little force need be applied to the anchor while inserting it in the hole, and then only at the very end of the inserting operation, so that there can be absolutely no chance of distorting the anchor .while it is being inserted in the hole.

What I claim is:

1. A machine screw anchor comprising an internally threaded expanding member having an exterior surface at one end tapering toward the other end, and an expansible member telescopically fitting over the expanding member, with one end engaging said tapered surface, and having a plurality of surfaceprojections whose outer and greatest peripheral boundary normally corresponds to a standard drill size, the said members being positioned so that at least one end of the expanding member must go into the anchor hole in advance of the expansible member, the expanding member having its hole-entering end, adjacent said tapered surface, smaller in diameter than the maximum diameter of the expansible member, as and for the purpose defined herein.

2. A machine screw anchor as set forth in claim 1, further characterized in that the said tapered surface has knurls thereon for the purposes described.

3. A machine screw anchor as set forth in claim 1, further characterized in that the hole-entering end of the expanding member has an annular flange adjacent the tapered surface.

4. A screw anchor comprising an internally threaded expanding member having an external taper adjacent one end, and an expansible member normally telescopically fitting over the expanding member onto the taper, the' said members being positioned so that at least one end of the expanding member must go into the anchor hole in advance of the expansible member, said expansible member having on its outer surface a plurality of projecting collapsible portions, the outer boundary of at least the projecting portions of greatest diameter being larger in diameter than the hole-entering end of the expanding member as and for the purposes described.

5. A screw anchor as set forth in claim 4, further characterized in that at least a part of the taper has longitudinally extending knurls thereon,v with a flange between the knurls and the adjacent extremity of the expanding member.

6. A screw anchor as set forth in claim 4, further characterized in that the projecting portions are in the form of substantially transversely spaced flutes of increasing diameter toward the drive end of the anchor.

'7. A screw anchor as set forth in claim 4, further characterized in that the projecting portions are such that the screw anchor will not be distorted on being inserted into a hole made with a worn drill which in its normal size would make a hole that would allow the anchor to be easily inserted therein.

8. In a screw anchor for the purposes described, including an internally threaded expanding member carrying an expansible member in telescopic relationship, the said members being positioned so that at least one end of the expanding member must go into the anchor hole in advance of the expansible member, means for compensating for wear of the drill used in making a hole for the anchor, said means comprising collapsible projecting portions on the outer peripheral surface of the expansible member, while the hole-entering end of the expanding member is normally smaller in diameter than that of a standard drill of a suitable size for the chosen anchor, at the end of its life of service.

9. A screw anchor for the purpose described including an internally threaded expanding memexpansible member, the expansible member ha?? ing collapsible projecting portions on its outer surface whereby greater variations may be permitted in the diameter of the hole made in masonry or the like for a given size anchor.

MAX L. SCHUL'I'E. 

